Page 174 - Clinical Pearls in Cardiology

162 Clinical Pearls in Cardiology

Supraventricular rhythms usually have narrow
QRS complexes in the ECG. A narrow QRS complex
(<120 milliseconds) reflects the rapid activation of the
ventricles via the normal His bundle-Purkinje system.
Thus, a narrow QRS complex suggests that the arrhythmia
is originating above or within the atrioventricular node.
A widened QRS complex (i.e. ≥ 120 milliseconds) can
occur in some types of SVT. This happens when there
are preexisting conduction abnormalities within the His
bundle-Purkinje system as in the case of supraventricular
tachycardia with aberrancy (e.g. WPW syndrome).
13. What do you know about ventricular tachycardia?
Ventricular tachycardia (VT) is a tachydysrhythmia
originating from a ventricular ectopic focus. It is
characterized by a rate typically greater than 120 bpm
with wide QRS complexes. VT may be monomorphic
(originating from a single focus with identical QRS
complexes) or polymorphic (may appear as an irregular
rhythm, with varying QRS amplitudes and morphology)
(Fig. 2).

Fig. 2: Ventricular tachycardia
14. What is slow ventricular tachycardia?
Slow ventricular tachycardia (also called as accelerated
idioventricular rhythm or AIVR) may be defined as